One year after their zombie comedy Mission: Impossible.

While it was by no means their first project, the rise of both Pegg and Wright can be traced back to the immense worldwide success of 2004's "rom zom com" Shaun of the Dead. Arguably the greatest zombie comedy of all time - and there's a surprisingly long list - Shaun of the Dead was co-written by Pegg and Wright, with Wright directing the film and Pegg playing titular protagonist Shaun. The film earned terrific reviews, and was also a box office hit, raking in $30 million on a budget of only $6 million.

Related: 10 Best Zombie Movies Of All Time

Shaun of the Dead was essentially a love letter to zombie cinema, as well as its pioneer writer/director Day of the Dead are also considered classics. Here's how the minds behind Shaun of the Dead ended up appearing in Romero's 2005 sequel Land of the Dead.

Simon Pegg & Edgar Wright's Land of the Dead Cameo Explained

Simon Pegg and Edgar Wright as Zombies in Land of the Dead

By the mid-2000s, it had been nearly two decades since 28 Days Later to reignite the sub-genre, despite not entirely being a zombie movie. 28 Days Later's success led Universal to produce Zack Snyder's well-received Dawn of the Dead remake in 2004, which was also a hit, leading Universal to reach out to Romero himself to get back in the game. The result was Land of the Dead, one of the fiercely independent Romero's fairly rare films made within the studio system.

It turns out that Romero was actually a big fan of Shaun of the Dead, and appreciated all the love Simon Pegg and Edgar Wright clearly had for the legendary director's work. He even wore a Shaun of the Dead pin on his shirt for the duration of Land of the Dead's shoot. With that in mind, Romero ed Pegg and Wright and invited them to the set. While there, he offered them small roles in the film, and Pegg and Wright naturally requested to be zombies. The two can be seen shackled inside a zombie photo booth, as pictured above. Pegg and Wright continued to be inspired by Romero, and paid public tributes to him upon the director's death in 2017.

More: How Night of the Living Dead Accidentally Became Public Domain